<p>From the maintainer's <a href="http://www.spamhaus.org/drop/" target="_blank">site</a>:</p>

<p><a href="?ipset=spamhaus_drop">spamhaus_drop</a> (Don't Route Or Peer) and EDROP are advisory "drop all traffic" lists, consisting of netblocks that are "hijacked" or leased by professional spam or cyber-crime operations (used for dissemination of malware, trojan downloaders, botnet controllers). The <a href="?ipset=spamhaus_drop">spamhaus_drop</a> and EDROP lists are a tiny subset of the SBL, designed for use by firewalls and routing equipment to filter out the malicious traffic from these netblocks.</p>

<p>EDROP is an extension of the <a href="?ipset=spamhaus_drop">spamhaus_drop</a> list that includes suballocated netblocks controlled by spammers or cyber criminals. EDROP is meant to be used in addition to the direct allocations on the <a href="?ipset=spamhaus_drop">spamhaus_drop</a> list.</p>

<p>When implemented at a network or ISP's 'core routers', <a href="?ipset=spamhaus_drop">spamhaus_drop</a> and EDROP will help protect the network's users from spamming, scanning, harvesting, DNS-hijacking and DDoS attacks originating on rogue netblocks.</p>

<p>Spamhaus strongly encourages the use of <a href="?ipset=spamhaus_drop">spamhaus_drop</a> and EDROP by tier-1s and backbones.</p>

<p>There is also a FAQ for the EDROP list <a href="http://www.spamhaus.org/faq/section/DROP%20FAQ" target="_blank">here</a>.</p>

